The present invention relates to hybrid powertrains for systems, for example for passenger vehicles, buses, trucks, boats, ships, trams, trains and similar. Moreover, the invention also concerns methods of controlling such powertrains, for example with regard to gear change. Furthermore, the present invention also relates to vehicles and similar including such powertrains. Additionally, the present invention relates to software executable on computing hardware for executing the methods of controlling such powertrains.
In recent years, considerable research has been invested in hybrid system technology in order to provide enhanced fuel economy as well as improved motive performance. Hybrid systems include hybrid powertrains, wherein each powertrain usually comprises a combustion engine, an electric machine arrangement, an electrical storage element and a transmission arrangement for coupling at least the electric machine arrangement to a load of the system. The electric machine is optionally implemented as a motor/generator. Superficially, such hybrid powertrains would seem to involve additional complexity and potentially added weight which would be deleterious to system performance. However, in practice several benefits arise from employing hybrid powertrains in comparison to conventional simple combustion engine systems which operate sub-optimally, especially in stop-start scenarios.
One considerable benefit provided by hybrid powertrains is rapid acceleration of a corresponding vehicle from standstill. Such rapid acceleration is achievable on account of electric motors being capable of developing relatively high starting torques, for example in the order of 1000 Nm, at low motor rotor rotation rates. Moreover, rechargeable batteries of hybrid power trains are capable of delivering enormous peak powers of several ten's or even hundred's of kiloWatts. In regard to vehicles equipped with such hybrid powertrains it is conventional contemporary practice to employ combustion engines in such hybrid powertrains to propel the vehicles when higher vehicle speeds have been attained whereat electric motors are not capable of providing any advantage. For example, combustion engines of hybrid powertrains are primarily used to provide motive power when their vehicles are cruising at high speeds on motorways. In urban traffic wherein frequent stop-start cycles are experienced, electric motors of hybrid powertrains are used to a considerable extent.
In a published international PCT patent application no. WO 97/15979, there is described a hybrid drive for a motor vehicle including an internal combustion engine coupled at its rotational output shaft via a clutch to an electric motor. The electric motor is, in turn, connected via a bridging coupling to an automatic gearbox and subsequently therethrough to wheels of the vehicle. The hybrid drive is alleged in the published application to improve considerably traveling comfort. By summing the rotational power developed by the combustion engine and the electric motor, it is alleged to be able to reduce a number of switching processes required in the hybrid drive during operation.
In a published U.S. Pat. No. 5,713,425, there is described a hybrid powertrain for an automotive vehicle. The powertrain comprises an internal combustion engine and transmission assembly providing a first selectable shiftable geared torque flow path to traction wheels of the vehicle. Moreover, the powertrain also comprises an electric motor-generator unit defining a second geared torque flow path that is located between the output of the first geared torque flow path and the aforesaid traction wheels. A control system is further included in the hybrid powertrain for operating the electric motor-generator unit to supply torque to the traction wheels while the torque flow in the first torque flow path is interrupted during the occurrence of a gear ratio change in the transmission assembly and during disengagement of a clutch. By way of interactive control of the internal combustion engine and the electric motor-generator unit, drivability of the vehicle is enhanced and engine exhaust gas emissions can be reduced. Additionally, the electric motor-generator can launch to vehicle into motion immediately in response to a request from an operator of the vehicle. During electric launch of the vehicle into motion, the interactive control of the combustion engine and the motor-generator permits the combustion engine to be restarted and then gradually take over a task of propelling the vehicle from the motor-generator unit.
In a published international PCT patent application no. WO2005/016681, there is described a method of controlling a drive unit of a motor vehicle. The drive unit comprises an internal combustion engine and an electric motor. A main transmission arrangement of the drive unit includes an output shaft that is rotationally coupled to a drive shaft of the motor vehicle. The transmission arrangement further includes an input shaft which is connected to the internal combustion engine. The electric motor is coupled to the input shaft or to the output shaft of the transmission arrangement via an intermediate transmission encompassing at least two transmission steps.
In operation, the vehicle is initially driven exclusively by the electric motor in order to accelerate the vehicle from a standstill coincident with the intermediate transmission being on its lowest transmission step. The combustion engine takes over the driving function prior to a shifting process of the intermediate transmission. The intermediate transmission is optionally implemented as a dog-clutch transmission.
The drive unit described in the aforementioned PCT application is well adapted for passenger cars operable to transport people seated within the cars.
The inventor has appreciated that such a manner of operation of the drive unit is suitable for vehicles such as passenger cars, but is sub-optimal for larger vehicles such as buses and trucks, especially when such buses and trucks are used in dense traffic in urban environments wherein frequent stop-start cycles are encountered. Moreover, in crowded buses, people are often standing on account of a lack of seating capacity which places further constraints that acceleration and deceleration of the crowded buses must be smooth and uniform without periods of loss of transmission power propelling the crowded buses. Such smooth transmission characteristics are obtained in contemporary hybrid powertrains in vehicles by using electric motors to initially provide acceleration of the vehicles and then invoking torque from combustion engines once the vehicles have attained appreciable speed prior to invoking a sequence of gear changes. However, the inventor has found that such contemporary hybrid powertrains are not capable of providing sufficiently smooth and uniform acceleration and deceleration.
Thus, the present invention is concerned with addressing a problem that contemporary powertrains are not capable of providing a sufficiently smooth and uniform acceleration.
It is desirable to provide an improved hybrid powertrain which is capable of providing more smooth and uniform acceleration, and correspondingly more smooth and uniform deceleration.
According to a first aspect of the invention, there is provided a hybrid powertrain including:
a combustion engine operable to output rotational power thereat;
an electric machine arrangement operable to output rotational power thereat;
a gearbox arrangement for receiving rotational power from at least one of the combustion engine and the electric machine arrangement, the gearbox arrangement being operable to couple corresponding motive power to a load;
a control unit arrangement coupled in communication with the combustion engine, with the electric machine arrangement and with the gearbox arrangement for coordinating their operation;
wherein the gearbox arrangement is operable to provide a plurality of gearing ratios;
characterized in that
the electric machine arrangement (60) is employable to extend a rotation rate range provided in a given gearing ratio at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto.
The invention is of advantage in that use of the electric machine arrangement to extend a range of rotation rates employable in at least the first gearing ratio is capable of reducing a frequency of gear changes, thereby providing for smoother and more uniform acceleration, and also smoother and more uniform deceleration. Such uniform deceleration is beneficially implemented as regenerative braking.
Optionally, in the hybrid powertrain, the electric machine arrangement is also employable to extend a rotation rate range provided in a given gearing ratio at both lower rotation rates when accelerating from a standstill or from a preceding gear.
There is also provided a hybrid powertrain including:
a combustion engine operable to output rotational power thereat;
an electric machine arrangement operable to output rotational power thereat;
a gearbox arrangement for receiving rotational power from at least one of the combustion engine and the electric machine arrangement, the gearbox arrangement being operable to couple corresponding motive power to a load;
a control unit arrangement coupled in communication with the combustion engine, with the electric machine arrangement and with the gearbox arrangement for coordinating their operation;
wherein the gearbox arrangement (200) is operable to provide a plurality of gearing ratios;
characterized in that
the electric machine arrangement (60) is employable to extend a rotation rate range provided in a subsequent gearing ratio at higher rotation rates after a gear change from a given gearing ratio to the gearing ratio subsequent thereto.
The present invention is beneficial during acceleration as well as during deceleration, for example when implementing regenerative braking to convert kinetic energy into electrical energy for storage in an energy storage arrangement.
The electric machine arrangement is beneficially couplable to an energy storage arrangement for providing electrical power to the electric machine arrangement in operation.
The powertrain is beneficially provided with a control arrangement for controlling operation of the powertrain. Further, the powertrain is beneficially provided with a coupling arrangement operable to couple rotational power between the combustion engine and the electric machine arrangement.
Preferably, in the powertrain, the coupling arrangement of the powertrain is operable to at least partially decouple the combustion engine from the gearbox arrangement at the higher rotation rates. More preferably, in the powertrain, the coupling arrangement is operable to fully decouple the combustion engine from the gearbox arrangement at the higher rotation rates. At least partly decoupling the combustion engine reduces a risk of damaging the engine by over-revving it and also is susceptible to reducing friction in the powertrain, thereby improving its efficiency.
Preferably, in the powertrain, the combustion engine is operable in each of the gearing ratios to deliver its maximum power at substantially a middle portion of the rotation range of the gearing ratio, with the electric machine arrangement providing its maximum towards lower and upper rotation rate limits of the gearing ratio. Such use of the electric machine arrangement at both rotation rate-limits of a given gearing ratio is in contradistinction to contemporary practice whereat power delivered from a combustion engine is normally used at relative higher rotation rates in the given gearing ratio.
More preferably, in the powertrain, the middle portion of the rotation range corresponds to an output shaft of the combustion engine rotating at rate in a range of substantially 1500 rpm to 3000 rpm, the lower rotation rate corresponds to an output shaft of the electric machine arrangement rotating at a rate in a range of 0 rpm to 1500 rpm, and the upper rotation rate corresponds to the output shaft of the electric machine arrangement rotating at a rate in a range of substantially 3000 rpm to at least 4500 rpm. Optionally, the lower rotation rate corresponds to the output shaft of the electric machine arrangement rotating in a range of 1000 rpm to 1500 rpm when the powertrain is already in motion.
According to a second aspect of the invention, there is provided a method of controlling a hybrid powertrain including:
a combustion engine operable to output rotational power thereat;
an electric machine arrangement operable to output rotational power thereat;
a gearbox arrangement for receiving rotational power from at least one of the combustion engine and the electric machine arrangement, the gearbox arrangement being operable to couple corresponding motive power to a load;
a control unit arrangement coupled in communication with the combustion engine, with the electric machine arrangement and with the gearbox arrangement for coordinating their operation;
wherein the gearbox arrangement is operable to provide a plurality of gearing ratios,
characterized in that
the method including steps of:
(a) employing the electric machine arrangement to extend a rotation rate range provided in a given gearing ratio at lower rotation rates when accelerating from a standstill or a preceding gearing ratio, and to extend a rotation rate range provided in the given gearing ratio at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto; or
(b) employing the electric machine arrangement to extend a rotation rate range provided in the given gearing ratio at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto.
Preferably, the method includes a step of using a coupling arrangement of the powertrain to at least partially decouple the combustion engine from the gearbox arrangement at the higher rotation rates. More preferably, in the method, the coupling arrangement is operable to fully decouple the combustion engine from the gearbox arrangement at the higher rotation rates.
Preferably, in the method, the combustion engine is operable in each of the gearing ratios to deliver its maximum power at substantially a middle portion of the rotation range of the gearing ratio, with the electric machine arrangement providing its maximum towards lower and upper rotation rate limits of the gearing ratio.
Preferably, in the method, the middle portion of the rotation range corresponds to an output shaft of the combustion engine rotating at a rate in a range of substantially 1500 rpm to 3000 rpm, the lower rotation rate corresponds to an output shaft of the electric machine arrangement rotating at a rate in a range of 0 rpm to 1500 rpm, and the upper rotation rate corresponds to the output shaft of the electric machine arrangement rotating at a rate in a range of substantially 3000 rpm to at least 4500 rpm.
According to a third aspect of the invention, there is provided a system including a hybrid powertrain according to the first aspect of the invention.
Preferably, the system is operable to control its hybrid powertrain using a method according to the second aspect of the invention.
Preferably, the system is a bus, a truck, a van, a passenger vehicle, a tram, a train, a boat, a ship, or a stationary power-delivering device.
According to a fourth aspect of the invention, there is provided a computer product executable on computing hardware for implementing a method according to the second aspect of the invention.
According to a fifth aspect of the invention, there is provided a computer product comprising computer program code means adapted to perform a method or for use in a method according to the second aspect of the invention when the computer program is run on a programmable microcomputer.
Preferably, the computer program is adapted to be downloaded to a powertrain according to the first aspect of the invention or one or more of its components when run on a computer which is connected to the Internet.
According to a sixth aspect of the invention, there is provided a computer program product stored on a computer readable medium, comprising computer program code means according to the fifth aspect of the invention.
According to a seventh aspect of the invention, there is provided a hybrid powertrain including:
a combustion engine operable to output rotational power thereat;
an electric machine arrangement, operable to output rotational power thereat;
a gearbox arrangement for receiving rotational power from at least one of the combustion engine and the electric machine arrangement, the gearbox arrangement being operable to couple corresponding motive power to a load;
a control unit arrangement coupled in communication with the combustion engine, with the electric machine arrangement and with the gearbox arrangement for coordinating their operation;
wherein the gearbox arrangement is operable to provide a plurality of gearing ratios;
characterized in that
the electric machine arrangement is employable to extend a rotation rate range provided in a given gearing ratio:
(a) at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto; or
(b) at both lower rotation rates when accelerating from a standstill or from a preceding gear, and at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto.
According to an eighth aspect of the invention, there is provided a method of controlling a hybrid powertrain including:
a combustion engine operable to output rotational power thereat;
an electric machine arrangement operable to output rotational power thereat;
a gearbox arrangement for receiving rotational power from at least one of the combustion engine and the electric machine arrangement, the gearbox arrangement being operable to couple corresponding motive power to a load;
a control unit arrangement coupled in communication with the combustion engine, with the electric machine arrangement and with the gearbox arrangement for coordinating their operation;
wherein the gearbox arrangement is operable to provide a plurality of gearing ratios,
characterized in that
the method including steps of:
(a) employing the electric machine arrangement to extend a rotation rate range provided in a given gearing ratio at lower rotation rates when accelerating from a standstill or a preceding gearing ratio, and to extend a rotation rate range provided in the given gearing ratio at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto; or
(b) employing the electric machine arrangement to extend a rotation rate range provided in the given gearing ratio at higher rotation rates prior to a gear change from the given gearing ratio to a gearing ratio subsequent thereto.
According to a ninth aspect of the invention, there is provided a method for controlling a hybrid powertrain having an electric machine arrangement operable to output or receive rotational power to/from a load via a gearbox arrangement, comprising the step of controlling the electric machine arrangement in an upper portion of a rotation range provided in a given gearing ratio provided by the gearbox arrangement.
Employing the electric machine arrangement in the upper portion of the rotation range provided in a given gearing ratio creates conditions for extending an available range of rotation rates from a combustion engine in a given gearing ratio. In this way, a frequency of gear changes may be reduced, thereby providing for smoother and more uniform acceleration, and also smoother and more uniform deceleration.
The wording “in an upper portion of the rotation range” corresponds to the wording “at higher rotation rates”. More specifically, the method comprises the step of controlling the electric machine arrangement to a rotational power connection to the load in the last portion of the rotation range, advantageously at 50-100% of the rotation range, preferably at 60-100% of the rotation range and especially at 70-100% of the rotation range. Preferably, the method comprises the step of controlling the electric machine arrangement toga rotational power connection to the load at rotation rates above 2000 rpm, especially above 2500 rpm and for example below 6000 rpm.
Preferably, the method comprises the step of controlling the hybrid powertrain so that the electric machine arrangement is the main power source in said upper portion of the rotation range and especially so that the electric machine arrangement is the only power source in said upper portion of the rotation range.
According to one preferred embodiment, the method comprises the step of controlling the electric machine arrangement to output rotational power to the load in said upper portion of the rotation range. Thus, the electric machine arrangement functions as a motor and supplies output rotational power, especially in order to accelerate the load. Preferably, the method comprises the step of controlling the electric machine arrangement to output rotational power to the load in the upper portion of the rotation range provided in the given gearing ratio prior to a gear change from said given gearing ratio to a higher gearing ratio. Thus, the method may comprise an upshifting in the gearbox. Preferably a plurality of consecutive upshifts is performed and the electric machine arrangement is controlled to output rotational power to the load before each upshift in said upper portion of the rotation range.
According to another preferred embodiment, the method comprises the step of controlling the electric machine arrangement to receive rotational power from the load, especially in order to decelerate the load. Preferably, the method comprises the step of controlling the electric machine arrangement to receive rotational power from the load in the upper portion of the rotation range provided in the given gearing ratio following a gear change to said given gearing ratio from a higher gearing ratio. Thus, the method may comprise a downshifting in the gearbox. Preferably a plurality of consecutive downshifts is performed and the electric machine arrangement is controlled to receive rotational power from the load after each downshift in said upper portion of the rotation range. According to one further development, a combustion engine in the hybrid powertrain may be disconnected from the load during the complete deceleration phase. Especially, the method comprises the step of controlling the electric machine arrangement to regeneratively brake the load.
Preferably, in addition to the electric machine arrangement, the hybrid powertrain comprises a further power source operable to output rotational power to the load via the gearbox arrangement. The further power source is constituted by a combustion engine and more particularly a diesel engine, but may alternatively be constituted by a fuel cell, gas turbine or other power source.
Preferably, the method comprises the step of controlling the further power source in a middle portion of the rotation range provided in the given gearing ratio provided by the gearbox arrangement. According to a preferred embodiment, the method comprises the step of controlling the combustion engine to a rotational power connection to the load in the interval 10-90% of the rotation range, preferably in 20-80% of the rotation range and especially in 30-70% of the rotation range. According to a preferred embodiment, the method comprises the step of controlling the combustion engine to a rotational power connection to the load at rotation rates in the range 500-3000 rpm and especially at rotation rates in the range 1000-2500 rpm.
Preferably, the method comprises the step of controlling the further power source to output rotational power to the load in the middle portion of the rotation range, especially in order to accelerate the load.
Preferably, the method comprises the step of controlling the hybrid powertrain so that the further power source is the main power source to output rotational power to the load in the middle portion of the rotation range and especially so that the further power source is the sole power source to output rotational power to the load in the middle portion of the rotation range. The electric machine arrangement may be controlled to give a contribution of output rotational power in said middle portion of the rotation range.
Preferably, the further power source is configured to output a rotational power up to a rotation rate limit in the vicinity of the upper portion of the rotation range and especially, the rotation rate limit is in a vicinity of a maximum speed of the further power source. Preferably, the limit of the upper portion of the rotation range substantially corresponds to the maximum speed of a combustion engine. However, the combustion engine may be able to operate at least partly in the upper portion of the rotation range. Hence, the electric machine and the combustion engine may output a rotational power simultaneously at least during a part of the upper portion of the rotation range. Further, the combustion engine may be configured so that it may deliver output rotational power also in the upper portion of the rotation range, but it is in fact disconnected from the load in the upper portion, and the method comprises solely using the electric machine arrangement in said upper portion.
Preferably, the method comprises the step of at least partially decoupling the further power source from the gearbox arrangement in said upper portion of the rotation range and especially fully decoupling the further power source from the gearbox arrangement in said upper portion of the rotation range. The decoupling procedure is preferably performed by means of a clutch.
Preferably, the further power source is operable in each of the gearing ratios to deliver its maximum power at substantially a middle portion of the rotation range of the gearing ratio, with the electric machine arrangement providing its maximum towards lower and/or upper rotation rate limits of the gearing ratio.
Preferably, the gearbox arrangement is operable to provide a plurality of gearing ratios.
Preferably, the method comprises the step of controlling the electric machine arrangement to a rotational power connection to the load via the gearbox arrangement also in a lower portion of a rotation range provided in a given gearing ratio when accelerating from a standstill or from a preceding gear.
It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention as defined by the accompanying claims.